The present invention relates generally to dispensers of volatilizable materials. More particularly, the invention relates to air fresheners for dispensing fragrant and/or deodorizing compositions in an enclosed area, such as the interior of a vehicle.
Currently existing air fresheners for vehicle interiors typically consist of a fragrance delivery system and a means for attaching the delivery system to the interior of the vehicle. The majority of these delivery systems use a cellulose pad saturated with perfume which, when exposed to the atmosphere, delivers fragrance via evaporation. The rate determining step for these delivery systems is evaporation from the pad.
Since Ficke's law teaches delivery rate from evaporation is dependent upon concentration, these systems deliver materials at an inconsistent rate, following first-order kinetics. This leads to very high levels of fragrance initially and an unacceptably low level of fragrance after only a short period of time.
The ideal air freshener delivery system would follow zero-order kinetics and have a delivery rate constant over time. This is difficult because perfumes typically have fifty to one hundred or more components, each with unique vapor pressures. The variation in vapor pressure causes each component to diffuse into the atmosphere at different rates. Approaching the ideal state is attainable by using transport phenomenon other than evaporation as the rate controlling step. One such system currently available is a low-density polyethylene membrane hermetically sealed to a reservoir. This type of system uses diffusion of the perfume's components through the membrane to greatly improve consistency of delivery over time. The drawback to these systems is the reduced delivery initially is too low to provide adequate performance.
It is an object of the present invention to provide a dispensing device which utilizes the consistent delivery of a membrane system but at the same time provides the user with the ability to increase or decrease intensity of delivery, as conditions require, throughout the life of the product.
It is another object of the invention to provide dispensing means which enable the user initially to dispense the perfume at a high rate of release to rapidly bring the aroma concentration within the interior of the vehicle up to a desired level and then to lower the rate of release to maintain the aroma concentration at the desired level.
It is a further object to provide a simple, uncomplicated dispensing device which can be manufactured economically from standardly available materials and which can be used immediately without the need for extensive directions.
Other objects and advantages will become apparent as the specification proceeds.